Grippers for use in clean rooms of the type with which the invention is concerned have previously been provided with means to attempt to eliminate contaminants as shown for example in U.S. Pat. No. 3,135,396, issued June 2, 1964 to Grainger. As shown in that patent a "bellows" type plastic bag is used in combination with a pair of pivoting gripper jaws. In such a device the bag, usually of PVC material, is captured at its ends in grooves in the jaws themselves and extends to enclose the entire manipulating apparatus. Such devices fatigue and are not long lived, in addition to not being readily adaptable for use in sliding jaw grippers.
Sliding jaw grippers per se are also known, as shown for example in U.S. Pat. No. 4,723,806, issued Feb. 9, 1988 to Yuda. That patent discloses a parallel robotic gripper having a vertically moveable member for opening and closing parallel gripping members which are carried on master jaws having lateral longitudinally extending slots therein for minimizing machining necessary to provide effective mounting for the slideable master jaws on longitudinally aligned horizontally spaced rails.
The cleanliness requirements for many processing and manufacturing tasks are becoming extremely strict. The environmental changes, and the type and amount of allowable contamination in each operation are monitored closely to ensure that quality products are made on a consistent basis. The principal users of clean rooms are advanced industries making use of thin film technology. The main products manufactured in ultraclean environments include VLSI semiconductors, compact discs, computer memory discs, magnetic and video tapes, precision mechanisms and pharmaceuticals.
Many of the processes which are performed in clean rooms are either partially or fully automated so that humans may be removed from the environment. It has been found that human beings are the single largest contributor to clean room particle contamination. Also, every piece of machinery which is used in a clean room must meet strict guidelines as to the size and amount of particles which it may release, and the materials used in its construction. These guidelines apply most strictly to the assembly machinery which will be situated near the products being produced, and to the manipulators used to handle and move the product.
Currently, the manipulators used to handle the products in a clean room are custom made or are modified to meet the cleanliness requirement. This is usually done at great expense and at a large sacrifice to the work envelope, and the performance of the automated workcell. The typical way of doing this is to enclose the entire manipulator inside of a bellows or enclosure as shown in the Grainger patent, and then to evacuate the entire set-up. The use of such "bellows" is a clumsy way of sealing because the bellows must be custom made in each case, and as already indicated does deteriorate at a rapid rate, adding to the particle contamination in the workcell. In most cases the standard production type grippers must also be modified to accept the bellows arrangement (as was true in the Grainger device which uses machined grooves to anchor the ends of the bellows). The necessary vacuum lines and porting used to evacuate the gripper inside the bellows are often set up awkwardly on the outer portions of the gripper, thus increasing the overall package size by 2-3 times.